| Penflufen developed by Bayer Crop Science,is a new fungicide of the pyrazole amide group,mainly used for seed treatment,and the registed covering in-furrow and seed piece treatments for potatoes,alfalfa,vegetables,and cereals.In this study,the environmental behavior including hydrolysis,photolysis,adsorption/desorption and degradation in different types of water and three contrasting soils of China was investigated for evaluating the environmental safety.In the present study,optimized QuEChERS and solid phase extraction were employed to develop a sensitive Ultra-performance liquid chromatography tandem mass-spectrometry detection(UPLC-MS/MS)method for quantification of penflufen in environmental waters and soils.The recoveries ranged from 87.8%to 109.5%for soils,and ranged from 70.6%-95.6%for waters,respectively.The established method is suitable for the determination of the residues of penflufen in soil and water,and the study of its degradation behavior in soil and water.The kinetics of hydrolysis of penflufen was studied in several aqueous buffers in the pH range 3-7 and in different temperature conditions.Penflufen was stable in acidic and neutral solution.Hydrolysis half-lives of penflufen in pH3,pH7 and pH 11 buffer were 449.8 d,392.7 d and 297 d,respectively.There was no significant difference in the hydrolysis rate of penflufen under 25?,35 ? and 50 ?conditions.The degradation half-lives were 383.8 d,389.5 d and 417.3 d,respectively.The photodegradation kinetics of penflufen in various conditions was investigated by UV and solar irradiation.Photolytic half-lives of penflufen in distilled water,tap water and river water were 221 h,165.9 h and 167.3 h,respectively.Photolysis half-lives in buffer solution of different pH(3,7,11)values were 181.8 h,159.9 h and 180.4 h,respectively.Adding high concentration of photosensitizer riboflavin,hydrogen peroxide and ferric ion could promote the photolysis of penflufen.Under natural condition,photolysis half-life of penflufen under solar light was 49.7 d.The photolysis rates of penflufen were characterized by a first-order kinetic model.The adsorption and desorption behavior of penflufen was studied.Freundlich equation was used to fit the adsorption isotherm of the reagent in three kinds of soil.The adsorption constants(Kf-ads)of penflufen in Beijing soil,Heilongjiang soil and Yunnan soil were 28.49,40.44 and 12.92,respectively,The adsorption capacity of soils for penflufen was Heilongjiang soil>Beijing soil>Yunnan soil.Adsorption isotherms of penflufen in Beijing soil and Heilongjiang soil belonged to L type isotherm,but for Yunnan soil belonged to S type isotherm.Adsorption free energy(?G)of penflufen in the three soils ranged from 14.47 t0 18.64 KJ/mol.It revealed that adsorption of penflufen in the soil belonged to physical adsorption process.The degradation kinetics of penflufen was investigated in three types of soil.Half-lives of penflufen were 71.5,59.2,and 203.9 days in Beijing soil,Heilongjiang soil and Yunnan soil under laboratory condition,respectively.In Beijing soil,dissipation rate of penlfufen was higher in non-sterile than it in sterile conditions.Under different soil temperature and moisture conditions,the dissipation of the pesticide was the fastest in 50 ? or field capacity soil.On the basis of the above findings,we proposed that penflufen was moderately stable in different soil types,and soil temperature,moisture,organic matter,and the microbial population were key factors influencing on the dissipation of penflufen in soil.The absorption and transform behavior of penflufen were investigated in wheat.Under root application condition,penflufen could quickly be absorbed by wheat plants,and quickly transferred to the stems and leaves.Under leaf spraying condition,penflufen could be quickly absorbed by the leaves,and transferred and accumulated to other leaves,then accumulated in the stem and root. |
PDF Full Text Request